Least detailed

Ilya Kurdyukov
https://github.com/ilyakurdyukov
Twitter: @ilyakurdyukov

The code for this entry can be found in prog.c

Judges' comments:

To use:

make prog prog_png prog_ppm
./prog Nrect infile outfile

Try:

# Take a selfie
./prog 1000 selfie.jpg output.jpg
# Admire your portrait in cubist style

(echo P6 1024 1024 255; dd if=/dev/urandom bs=3M count=1) > random.ppm
# Look at random.ppm. Do you see any patterns?
./prog_ppm 1000 random.ppm output.ppm
# See which patterns the program has found

for i in 0001 0002 0004 0008 0016 0032 0064 0128 0256 0512 1024 2048 4096 8192 ; do ./prog $i sample.jpg out$i.jpg; done
# Then flip through the out*.jpg pictures and see when you start recognizing the image.

Selected Judges Remarks:

This entry has reminded us of a winning entry back in the early 90s. Can you guess which one?

For a given image, try graphing the execution time relative to the number of rectangles. What is the complexity? Is it obvious from the source code?

Author’s comments:

Usage

This program divides the image into a specified number of rectangles. This process is content aware, so algorithm tries to match most of the information. However, it doesn’t finds the best theoretically possible layout.

./prog 1000 input.jpg output.jpg

Building

You can build three versions, depending on the image format.

Default is JPEG version, if you have the libjpeg development package installed in your system, then make without arguments should do the thing.

If you want to use libjpeg compiled from sources, then use LIBS define to specify the path to includes and the library.

make prog LIBJPEG="-Ijpeg-6b jpeg-6b/libjpeg.a"

Use this command to build a PNG version (you need libpng):

make prog_png LIBPNG="-lpng"

And the PPM version (no additional dependencies, can read raw/ASCII PPM, writes raw PPM):

make prog_ppm

Building on OSX

Thanks to Cody Ferguson for this information!

First, make sure you have the compiler tools installed e.g. by:

$ sudo xcode-select --install

Make sure you install MacPorts. Then do:

$ sudo port install jpeg libpng ImageMagick

The program itself doesn’t need ImageMagick, install it only if you plan to make gifs from the results using “makegif.sh”.

After that’s installed you need to run make with these options:

$ make LIBS="-I/opt/local/include -L/opt/local/lib"

Notes

Made this thing while experimenting with the idea of representing an image with rectangles (lossy compression). It’s not very good in that sense, but the results look funny, like a kind of cubism pixelart.

Do not use values above 50000, it gonna be slow.

To understand how this works, just try running with 1,2,3,4… number of rectangles. At each iteration, the rectangle with the biggest difference from the picture data is split (halves may have different size) horizontally or vertically to get the minimum difference.

You can use this command to make a gif from output images (uses ImageMagick):
convert -delay 10 -dither none -loop 0 $(ls out*.png | sort -V) $(ls out*.png | sort -rV) +map out.gif
Also provided makegif.sh to aid with gif creation.